The present invention relates to a magnetic disk equipment using a dynamic pressure slide bearing.
Following remarkable spread of a personal computer, the magnetic disk equipment needs high recording density, large capacity, small size and high speed. The magnetic disk equipment, that is used for a personal computer, needs high speed and high precision of the rotation more and more. Ball bearings were used for the motor for a magnetic disk drive conventionally. Improvement of the manufacture precision and the lubrication, etc. in the ball bearings has raised rotary precision.
But the ball bearings have a limit to the improvement of manufacture precision. Rotary precision is deteriorated by wear of bearing surfaces. A transformation is easy to arise in the inside and outside ring in assembly of a motor, when the ball bearings of a small diameter are used for miniaturization of equipment. The limit of high recording density arises by the above reason. There is a motor that adopts a dynamic pressure slide bearing instead of ball bearings. This motor is disclosed in the Japanese patent Laid-open print No. 5-336697 official gazette. The motor that adopts a dynamic pressure slide bearing has the problem of the oil leakage from the bearing part and scattering of oil particles. The seal structure of a dynamic pressure slide bearing is disclosed to the Japanese patent Laid-open print No. 7-310830 official gazette.
The magnetic disk equipment for the personal computer of a desk top type and a notebook type is easy to handle it, and it is necessary to endure an impact when it falls from the top of a desk and during a portage. When magnetic disk equipment receives 500-1000 G impact, the intensity of the structure parts is deteriorated, and measured precision changes. In case of the magnetic disk equipment using dynamic pressure slide bearing equipment, the oil scattering from the bearing equipment occurs, and the function is sometimes harmed.
The structure that refers to the seal of bearing equipment is disclosed to the Japanese patent Laid-open print No. 8-310830 official gazette. This seal is used for the oil leakage measures of bearing equipment. But it is not considered against oil pollution of magnetic disk equipment. To increase rotary precision, a motor using a dynamic pressure bearing is disclosed to the Japanese patent Laid-open print No. 5-336697 official gazette. But when a spindle motor is installed in magnetic disk equipment and it is rotated, fluid power operates on a spindle motor in the axial direction. This fluid power is generated by the flow of the air between rotary parts such as the magnetic disk and the stillness part. At this time, because the flow of the air is not uniform, the fluid power fluctuates and sometimes harms the rotary precision of the axial direction.
Therefore, the fluid power of the axial direction that acts on the spindle motor for high recording density of the magnetic disk equipment must be reduced. A conventional spindle motor for the magnetic disk drive is positioned to the axial direction by force that attracts magnetically. But a conventional spindle motor does not consider the fluid power and the fluctuation of the fluid power that occur by the rotation of the magnetic desk.
It is an object of the invention to prevent pollution of the magnetic disk by the oil leakage and scattering of the oil particles from the bearing equipment.
Another object of the invention to provide the magnetic disk equipment with high reliability that does not generate the fluid power and the fluctuation of the fluid power that occurs by the rotation of the magnetic desk.
The present invention has a motor drive part and magnetic fluid bearing structure using the dynamic pressure slide bearing inside a hub on which the magnetic disk is mounted. A passage of the axial direction for air circulation is built in the hub. As a result, the fluid power and the fluctuation of the fluid power of the axial direction that acts on the spindle motor during the rotation is reduced, and the rotary precision of the axial direction is improved. To prevent the oil leakage from the bearing equipment, magnetic fluid is used as a lubrication fluid of the bearing. And magnetic fluid is magnetized with the permanent magnet arranged in the bearing equipment.
By preparing the spiral groove to generate the dynamic pressure in the opening of bearing equipment or in the face of hub that is opposed to this opening, the oil particle is prevented from rushing outside the bearing equipment. In case magnetic fluid leaks outside the bearing equipment by impact force that operates on magnetic disk equipment, the magnetic fluid leaked is recovered in the bearing equipment along the spiral groove by using the rotation of hub.
A hollow of a ring-form is provided in the hub in the neighborhood of the connection of the hub and the rotary axis. In case magnetic fluid leaks outside the bearing equipment by impact force that operates on magnetic disk equipment, the magnetic fluid leaked is held in this hollow. As a result magnetic fluid is prevented from scattering.
The passage for the air circulation that penetrates the axial direction was built in the hub on which the magnetic disk is mounted. As a result the fluid power of the axial direction that acts on the hub and the fluctuation of this fluid power can be suppressed. Because the rotary precision of the axial direction can be raised, the recording density of magnetic disk equipment improves. The groove for dynamic pressure generation was prepared in the opening of bearing equipment. The hollow of a ring-form was provided in the press fitting part of the hub and the axis. As a result, leakage of magnetic fluid that was enclosed in the bearing equipment and scattering of the oil particles can be prevented during the rotation. Leakage of magnetic fluid that was enclosed in the bearing equipment and scattering of the oil particle can be prevented even if impact power operates on magnetic disk equipment. Pollution of the magnetic disk is prevented, the precise spin of the magnetic disk can be maintained, and the life of the magnetic disk becomes long. By the above, magnetic disk equipment with a high recording density and with high reliability can be provided.